n Southern African Forestry Journal - The effects of remedial fertilizer treatments on growth and pulp properties of stands established on infertile soils of the Zululand coastal plain : scientific paper




Remedial fertilizer applications were applied to nutrient-poor stands of <i>Eucalyptus grandis&lt;/i&gt; growing on infertile (ex-agricultural) land of the Zululand coastal plain. Two nitrogen-rich fertilizer mixtures were applied in one year-old stands at rates ranging from zero to 160 kg N ha&lt;sup&gt;-1&lt;/sup&gt; . Foliar nitrogen levels increased highly significantly at the higher levels of fertilization. A highly significant response to height, diameter and basal area growth was observed within 6 months of treatment initiation which was sustained until clear felling (8.3 years). A comparison of the unfertilized control with the optimum treatment (i.e. a single fertilizer dose equivalent to 80 kg N ha&lt;sup&gt;-1&lt;/sup&gt; ) yielded the following results: Utilizable wood volume increased from 136.7 to 264.3 m&lt;sup&gt;3&lt;/sup&gt; ha&lt;sup&gt;-1&lt;/sup&gt; . The wood density showed a weakly significant increase from 448 to 472 kg m<sup>-3</sup>. The pulpability factor (defined as the pulp yield / kappa number) decreased significantly from 2.63 to 2.32. The net effect of fertilization on pulping properties is a non- significant increase in pulp yield per unit volume of timber (chiefly due to increases in wood density). The combined effects of fertilization on both volume growth and pulping properties resulted in an increase in the pulp yield on a plantation area basis from 32.03 to 63.43 t pulp ha&lt;sup&gt;-1&lt;/sup&gt; in the 8.3 year-old stand.


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